Fractionation and separation of cells from suspensions such as blood or bone marrow is becoming more and more part of medical treatment. For such treatment, cells are extracted from a patient, then separated to provide the desired target cells, which are usually stimulated or manipulated or expanded before introducing into the same or a different patient. Extracting, preparation, fractionation, separation, manipulation and introducing of the cells should be performed as fast as possible to reduce stress imposed on the target cells and the patient. Optimally, the entire process is performed on-site at the patient.
Fractionation and separation of cell suspensions by centrifugation is long known in the art to separate samples of biological origin into two or more components. Centrifugation systems, especially centrifugation chambers can be optimised for the type of sample to be separated, for processing speed, separation quality or the amount of material to be processed.
For separation of cells from a suspension such as blood by centrifugation, it is beneficial to monitor the separation process and to provide the centrifugation chamber with appropriate input/output ports. In this respect, International Patent Applications WO 2009/072006 and WO 2009/072003 incorporated herein by reference in their entireties disclose a centrifugation system and a centrifugation chamber with means for controlling the separation process, and at least one input and output port located in the rotational axis of the centrifugation chamber. The centrifuge and chamber of WO 2009/072006 and WO 2009/072003 allow continuous centrifugation, wherein sample, media, gases and other materials can enter and leave the system e.g. through inlet and outlet ports without stopping the centrifugation process and refilling the centrifuge.
U.S. Pat. No. 5,837,150 discloses an apparatus comprising in inner and outer sidewall, wherein blood can be separated in a plurality of layers by centrifugation. The blood and the separated layers can enter and/or leave the chamber through openings of the inner sidewall, which are covered by shields located against the direction centrifugation. A centrifugation chamber with an inner and outer sidewall and openings in the inner sidewall is complicated to manufacture. Since the shields of the openings in the inner sidewall are located against the direction centrifugation, the speed of removal of liquids will be low.
U.S. Pat. No. 5,879,280 is directed to a centrifugation chamber with barriers to build up a pool of liquid which is drained for removal from the chamber. Building a pool of liquid will allow re-mixing of already separated layers ad poor separation quality will result. Furthermore, since the barriers are located against the direction centrifugation of flow, the speed of removal of liquid from the chamber will be low.
Any separation process by centrifugation involves at least the steps of providing a cell suspension into the centrifugation chamber, separation of the liquid into several layers according to their density and draining the separated layers from the chamber into different containers.
The quality of the separation step, i.e. the purity of the layers in the chamber, can be influenced by centrifugation time and applied gravity forces (i.e., the speed of rotation of the chamber).
Regardless of the purity of the layers during the centrifugation step, it was observed that separated layers were in part mixed again during draining of a layer, especially if the speed of draining is too high. Reducing the speed of draining would reduce re-mixing of adjacent layers but result in an undesired longer processing time.
Accordingly, there is a need to improve the centrifugation process in terms of processing speed and separation quality.
WO 2009/072006 discloses in FIG. 2A a centrifugation chamber with a deflector shield. The deflector shown has a width of about ⅓ of the circumference of the chamber. The purpose of this deflector is not described, but a deflector of this size prevents the separation of the sample into layers during centrifugation. The chamber as shown in FIG. 2A of WO 2009/072006 is not suitable for separation of samples into layers by centrifugal forces.